Arcanum Oculi

A small floating arcane eye that shines an eerie arcane blue colour, it hovers and floats around your head.

This small eye hovers and floats around your head, it is immune to all damage that isnt specifically targeted at it, it has an AC of 15 and a HP of 20, it is immune to necrotic and psychic damage.

While attuned to this eye you have advantage on perception checks and cannot be flanked.

At the start of each day you may choose to store some of your spell slots into this eye, up to an amount of spell levels equal to your Spellcasting ability score + Proficiency Bonus, and it stores the amount and levels of the spells.

At the end of one of your turns the eye can consume those slots to cast a spell equal to that level from the wizard spell list no action required by you.

As a Reaction when you are the target of an attack or required to make a saving throw, it can expend those spell slots to increase your AC or that Saving throw by that amount until the start of your next turn.

If the eye is destroyed it goes dormant until you next complete a long rest, upon doing so you can expend 10 levels of spell slots to reawaken the eye, these slots are not stored by the eye but are considered expended. The first time you attune to it, it awaken automatically. 

Notes: Advantage: Perception, By a Spellcaster